A known type of tobacco shredding apparatus comprises a rotary carrier for one or more knives which cut tobacco shreds for use in making cigarettes from the leading face of a continuous cake of compacted tobacco. The cake is formed and its contents compacted by a feeding device comprising upper and lower feed conveyors which define a gradually narrowing path extending from a source of threshed tobacco lamina to a comminuting station where the leading face of the cake is squeezed between upper and lower pressure applying elements and moves into the range of the orbiting knives.
Conventionally an automatic feeding system is used to provide the source of tobacco leaves, comprising an upwardly-extending hopper into which the tobacco lamina are dumped. A reciprocally-movable end wall in the hopper opposite to the upstream throat of the conveyors is provided to assist in propelling the tobacco lamina into the throat. Such apparatus is shown in U.S. Pat. No. 4,090,521. The tobacco lamina are compressed somewhat by the gravitational force of the head of lamina in the hopper so as to increase the throughput of the shredding apparatus over what otherwise would be the case.
The latter procedure suffers from a number of drawbacks. The tobacco lamina enter the apparatus through a vertically-extending hopper and tend to assume a horizontal orientation. The rear wall movement required to move the lamina into the throat causes the tobacco to move towards a vertical orientation for movement between the compaction conveyors to the cutter. This effect results in the necessity to apply considerable pressure on the cake of tobacco at the cutter to prevent whole tobacco lamina from being pulled out uncut. The application of this pressure adversely affects the filling power of the tobacco.
The filling power of cut tobacco is its ability to fill a cigarette tube. The greater the filling power, the harder is the cigarette for the same quantity of tobacco. For the economic production of cigarettes, it is desirable for the filling power to be as high as possible. In the prior art procedure noted above, the tobacco tends not to be evenly distributed across the width of the compaction conveyors and, in particular, the tobacco at the sides tends to be less compact than in the middle. This phenomenon requires the exertion of even greater pressure on the tobacco cake at the cutters in excess of that required in the middle, so that tobacco lamina pull-out at the sides does not occur, thereby further adversely affecting the filling power of the tobacco.
The problem that is solved by the present invention is how to provide the same throughput to tobacco through the tobacco shredding apparatus while at the same time decreasing the pressure requirement at the cutter and thereby improving the filling power of the cut tobacco.